The Pentax SMCP-DA 17-70mm f/4 AL (IF) SDM Lens is a high-quality fixed-aperture f/4 lens designed exclusively for use with digital SLR cameras. This lens brings together advanced optical technologies, including aspherical elements, special optical-glass elements, and original lens coatings. It offers a versatile wide to medium-telephoto zoom range, and allows for a wider range of shooting applications over the more standard zoom lenses.
This lens comes equipped with the SDM focusing system, which assures smoother and quieter auto-focusing operation by using a built-in supersonic motor. Since this lens only has electrical contacts to communicate between the lens and the camera, autofocusing will only be possible with DSLR cameras that support SDM (e.g. K10D, K20D, K100D Super, K200D, and later models). When mounted on older Pentax digital SLR camera bodies, only manual focusing will be possible.